In the integrated circuit industry today, hundreds of thousands of semiconductor devices are built on a single chip. Every device on the chip must be electrically isolated to ensure that it operates independently without interfering with another. The art of isolating semiconductor devices has become an important aspect of modern semiconductor technology for the separation of different devices or different functional regions. With the high integration of the semiconductor devices, improper electrical isolation among devices will cause current leakage, and the current leakage can consume a significant amount of power as well as compromise functionality. Among some examples of reduced functionality include latch-up, which can damage the circuit temporarily or permanently, noise margin degradation, voltage shift, and cross-talk.
Shallow trench isolation (STI) is one of the preferred electrical isolation techniques especially for a semiconductor chip with high integration. Broadly speaking, STI techniques involve the formation of shallow trenches in the isolation areas or regions of a semiconductor wafer. The shallow trenches are then filled with dielectric material such as silicon dioxide to provide electrical isolation between devices subsequently formed in the active regions on either side of the filled trenches.